1. Field of the Invention
The present invention relates generally to a mold clamping mechanism of an injection-molding machine, and more particularly, to a detecting apparatus capable of automatically and accurately detecting a die-touch position of a direct mold clamping mechanism which is driven by means of a servomotor.
2. Description of the Related Art
In a known motor-operated direct mold clamping mechanisms a movable platen disposed between a stationary platen and a rear platen is driven for mold clamping by means of a servomotor which is connected to the movable platen through a transmission mechanism. In the mold clamping apparatus of this type, a predetermined mold clamping force is produced by driving a movable die additionally for a predetermined distance in the direction for pressure contact, from a position where the movable die is in contact with a stationary die. Also, a mold opening end position, a die protection start position, etc. are determined on the basis of the die-touch position. In order to produce the predetermined mold clamping force and to perform a specified die opening/closing operation, therefore, the die-touch position must be detected and set accurately. Since the die-touch position varies depending on the thickness of the dies, moreover, it must be detected and set every time the die thickness is changed.
Conventionally, in detecting the die-touch position, an operator visually determines whether or not the die-touch position is reached by the movable platen, and manually adjusts the location of a limit switch for die-touch position detection so that the limit switch is turned on when the movable platen reaches the die-touchy position. In this case, it is difficult to accurately determine the arrival at the die-touch position. For example, a movable die position in which a mold clamping force of a certain size is already produced may be mistaken for the die-touch position. In consequence, the die-touch position cannot be detected and set accurately, so that satisfactory products cannot be manufactured. Moreover, the fine manual adjustment of the location of the limit switch is so troublesome that the efficiency is lowered.